This invention relates to an improved sewing system that is more economic and simpler to construct, has improved operating characteristics, and is more versatile in its uses than prior sewing machines of this type. The sewing machine of this invention will be described in connection with twin needle sewing apparatus. The apparatus is illustrated and described in connection with the operation of stitching belt loops to the waistband of blue jean type trousers, although its use is not restricted to that type of operation.
The sewing system of this invention is smaller than the usual industrial type sewing machine, and has a cloth holder that is suspended from the upper horizontal arm rather than being supported on the base. The cloth holder in a presently preferred embodiment is automatically controllable in the X-Y-Z directions. In keeping with its smaller structure, the up-down motion of the cloth or workpiece clamp that is associated with the cloth holder is solely vertical rather than being along an arc of a pivot arm as is common in the prior art.
In prior art sewing machines that employ twin needles spaced apart on a horizontally extending needle clamp, it has been found that the single needle bar and needle clamp will bend and deflect as a result of the needles being deflected as they penetrate anywhere from 6 up to 14, for example, layers of heavy cloth of the belt loop and waistband. In this invention I overcome that problem by employing two symmetrically spaced needle bars to support and actuate the needle clamp member.
Rather than having the main frame or housing of the machine made of one or more castings or extrusions as in the prior art, the vertical and base arms of the sewing machine of this invention are made up respectively, of short members of tubular steel stock and a short U-shaped channel member. The top arm is a short milled block. The individual short members or arms are joined together to make the frame. The use of the individual short members avoids having to machine a large, bulky, and irregularly shaped castings as was required in constructing the conventional industrial sewing machines of the prior art. All necessary machining is done on the individual short members before they are joined together to form the rigid, integral frame.